Field of the Invention
The present invention relates to passive magnetic bearing systems, and more specifically, it relates to the utilization of static electrostatic forces between specially designed electrode configurations to overcome limitations imposed by Earnshaw's Theorem.
Description of Related Art
Current techniques for overcoming Earnshaw's Theorem include “active” magnetic bearings having position sensor-controlled electromagnets, and the Lawrence Livermore National Laboratory (LLNL) passive magnetic bearing systems that take advantage of electrodynamic forces from rotating Halbach permanent magnet arrays interacting with specially configured stator windings. Such stabilizers obviously cannot function at zero speed, and thus they require the use of retractable mechanical bearings in operation.
The essence of Earnshaw's theorem, when it is applied to magnetic forces between permanent magnets, is that it proves that in static equilibrium it is impossible to stably levitate a permanent magnet element through the forces exerted by any fixed configuration of other permanent magnets. Earnshaw's Theorem also applies to electric charges, where it asserts that no fixed configuration of static charges can be found that will stably levitate another static charge. Past approaches to overcoming the magnetic version of the theorem, such as those described by the present inventor in U.S. Pat. No. 5,495,2212 and U.S. Pat. No. 5,847,4803 have been based on the long-accepted premise that Earnshaw's Theorem can only be overcome through the use of dynamic effects, i.e., either those of sensor-based feedback systems, as they are employed in so-called “active” magnetic bearings, or through the use of rotation-dependent stabilizing forces, as described in the above-listed patents. A technique for stabilization that does not depend on dynamic effects is desirable. It would be beneficial if such a system, when used in magnetically levitated rotating systems, e.g., flywheel energy storage systems, could operate equally well at any rotation speed, including zero speed. The present invention provides these benefits.